Bleaching composition

ABSTRACT

In a method for preparing dry stable bleaching and oxidizing compositions containing at least one peroxygen compound and at least one organic acid anhydride, the improvement which comprises: absorbing the organic acid anhydride on a particulate inert absorbent material, providing said absorbed material in a predetermined granulated size range, and mixing said granulated product with at least one peroxygen compound to prepare a novel solid bleaching and oxidizing composition which is stable over prolonged periods of time.

United States Patent Moyer et al.

Feb. 1, 1972 [54] BLEACHING COMPOSITION [72] inventors: John R. Moyer; William G. Moore, both of Midland, Mich.

[73] Assignee: The Dow Chemical Company, Midland,

Mich.

[22] Filed: Mar. 12,1968

211 Appl. No.: 712,363

3,372,l25 3/l968 Hill ..2S2/l86 Primary Examiner-Riehard D. Lovering Assistant Examiner-4min Gluck Attorney-Griswold & Burdick, C. Kenneth Bjork and Bruce M. Kanuch [5 7] ABSTRACT In a method for preparing dry stable bleaching and oxidizing compositions containing at least one peroxygen compound and at least one organic acid anhydride, the improvement which comprises: absorbing the organic acid anhydride on a particulate inert absorbent material, providing said absorbed material in a predetermined granulated size range, and mixing said granulated product with at least one peroxygen compound to prepare a novel solid bleaching and oxidizing composition which is stable over prolonged periods of time.

14 Claims, No Drawings BLEACHING COMPOSITION BACKGROUND It is well known in the art that aqueous solutions or organic monoperacids and/or persalts of such acids possess bleaching and oxidizing properties. Also, there exists stable dry solid compositions which when dissolved in aqueous solutions yield these organic peracids and/or salts in situ. These dry solid compositions usually consist of a particulate mixture of at least one peroxygen compound and at least one organic acid anhydride. It is usually preferred to maintain these compositions in a free-flowing granulated form for ease in measuring required amounts and ease of packaging and the like. The compositions are sufficiently water-free so as to prevent a chemical reaction between the components of the mixture prior to their use for bleaching or oxidizing purposes.

These granulated dry compositions tend to deteriorate upon standingbecause of the low-melting point and hydroscopic characteristic of some of the organic acid anhydrides employed therein. Upon deterioration the compositions fuse and form a solid agglomerate thus making it difficult to take measured quantities, dissolve the compositions in aqueous solutions, and remove the compositions from their containers. This is especially prevalent when benzoic anhydride is employed since it has a melting point of only about 108 F. lt has now been discovered that if the anhydride is absorbed on a substantially inert absorbent and provided in an appropriate particulate size range that the stability of the dry composition is greatly increased, thereby maintaining the compositions in a preferred granulated form over sustained periods of time.

SUMMARY The present invention concerns an improvement in the method of preparing dry solid bleaching compositions containing at least one peroxygen compound and at least one organic anhydride and to novel dry solid bleaching compositions thereof. The present improvement consists in absorbing an organic anhydride on a substantially inert absorbent material and providing said absorbed material in a particulate form of a predetermined size range. The absorbed anhydride material is mixed with granules of an appropriate peroxygen compound and other constituents to provide novel dry bleaching compositions stable over sustained periods of time. All the constituents are usually provided in a granulated form having approximately the same size range to provide a free flowing product. However, it is understood that the various components may be compressed or packed into predetermined forms containing the constituents evenly distributed therethrough or compacted in forms having layers or concentrated areas containing only one constituent in each area or other similar shapes such as tablets, rolls, balls and the like.

PREFERRED EMBODIMENTS Usually, in the practice of the present invention, an organic anhydride such as, for example, benzoic anhydride is absorbed on a particulate inert absorbent material by melting the anhydride and contacting it with the inert absorbent. Usually it is preferred to spray a molten anhydride onto an inert absorbent provided in a predetermined granulated size range. The anhydrides can also be absorbed on the inert absorbent by first dissolving the anhydride in an inert solvent of .low volatility, such as, for example, methylene chloride, slurrying the inert particulate absorbent in said solvent and evaporating the solvent thus leaving the anhydride absorbed on the inert absorbent. Usually the inert absorbent material and the organic anhydride are combined in amounts to provide a granulated product containing from about 30 to about. 65 percent by weight of the inert absorbent material and 35 to 70 percent by weight of the anhydride. The exact quantity of inert absorbent required will depend upon the oil sorptive capacity of the particular inert absorbent employed. A sufficient amount of the inert material should be employed, however, so as to provide a free flowing product at temperatures above about [08 F.

Usually about 35 to about 50 percent by weight of inert absorbent in the granulated product is preferred.

The technique employed for providing the absorbed anhydride-inert material in granulated form is not ordinarily critical to improving the stability of the final product. However, the particle size does govern the resultant stability and larger sizestare preferred, since they reduce the surface to mass ratio of the active ingredients in the granulated compositions and thus impart a high-temperature stability to the bleaching compositions. The size of the particles should be as large as possible while still sufficiently small such that a substantially homogenous mixture of the granulated components of the bleaching compositions may be made. Usually the particles should range in size from about 5 to about mesh (U.S. Standard Sieve). Particles ranging in size from about minus 8 to plus 20 mesh have been found to be particularly useful in providing a product which can be readily admixed with the other components of dry' solid bleach compositions and are stable for sustained periods of time.

lnert absorbent materials which have found particular utility in the present invention include, for example, diatomaceous earths; synthetic silica-alumina compounds; certain metal salts, such as sodium sulfate, magnesium sulfate, calcium sulfate; and certain substantially inert clays such as, for example, kaolinite-type clays, montmorillonite-type clays, vermiculite, attapulgus clay, Fullers earth, and the like. An especially useful absorbent consists of an expanded perlite material. Expanded perlite consists of the product obtained from the thermal treatment of the glass appearing perlite rock usually composed of SiO Al O water, potash, soda and lime in varying proportions. When the perlite rock is heated to its softening point it expands to form a light fluffy material similar in appearance to pumice rock. The expanded perlite can be processed, such as by grinding, to provide perlite material in various particulate size ranges. As employed in the present invention the inert absorbent material should be soluble in aqueous solutions or have a particle size which is small enough to pass through woven fabrics.

As indicated, the present invention concerns an improve ment in dry solid bleach compositions which yield organic monoperacids or salts thereof when dissolved in an aqueous media. These dry bleach compositions usually consist of a dry stable particulate mixture of at least one solid inorganic peroxygen compound and at least one solid organic acid anhydride. Examples of operable inorganic peroxygen compounds include, the inorganic perborates, peroxides, percarbonates, perphosphates and the like. Sodium perborate monohydrate has been widely used because of its low cost and availability. Potassium perborate and ammonium perborate are especially desirable because of their stability for sustained periods of time. Among other specific peroxygen compounds which may be included are urea peroxide, zinc peroxide, magnesium peroxide and calcium peroxide. These peroxygen compounds may be either anhydrous or in the hydrated form as long as they are sufficiently free of uncombined water so as to be unreactive toward the organic acid anhydride in a dry mix prior to use.

Also included in the commonly used dry bleach compositions is a solid organic acid anhydride. Examples of suitable anhydrides include succinic anhydride, maleic anhydride, phthalic anhydride, glutaric anhydride and benzoic anhydride. Generally nontoxic organic acid anhydrides are employed; however, anhydrides of a toxic nature may be employed if desired.

Other ingredients may also be employed in the dry solid bleach compositions to modify the properties of the monoperacid solutions which are produced. For example, the pH of the final peracid may be controlled to an extent by incorporating certain alkaline or acid materials such as, for example, anhydrous sodium carbonate, tetrasodium pyrophosphate and other similar compounds. Other desirable properties may be imparted to the peracid solutions by incorporating into the dry composition other substances such as soaps, perfumes and other materials which are not detrimental to the bleaching and oxidizing properties of the compositions.

The dry bleach compositions usually contain equimolar quantities of the peroxygen compound and organic acid anhydride. However, the acidity and alkalinity of the prepared solutions may be varied by employing other than equimolar ratios of the ingredients.

The peracids offer a rapid and powerful bleaching and oxidizing media which can be used for industrial purposes, such as, for example, in the bleaching of textiles and wood pulp and for consumer use such as for bleaching textiles.

The following examples facilitate a more complete understanding of the present invention but are not meant to be limiting thereto.

EXAMPLE 1 One part by weight of molten benzoic anhydride was absorbed onto 1.2 parts by weight of diatomaceous earth. Upon cooling, a free flowing powder formed which retained its solidlike appearance well above the melting point of benzoic anhydride (i.e., about l08 F.). After cooling the powder to room temperature, the powder was compacted into tablets and pulverized into fine granules. These granules were screened into four fractions as set forth in following table I. A portion of each fraction was dry blended with half its weight of sodium perborate monohydrate. The four fractions were maintained in open containers at 122 F. for various periods of time. The samples were analyzed by infrared techniques periodically to determine the percent of unreacted benzoic anhydride remaining in each. The results and time periods are tabulated in following table I.

TABLE I Particle Size of Benzoic anhydridediatomaceous earth particles Percent of unreacted Benzoic anhydride Initial 4 l 1 days days 78 66 Sample I 72 SI 24 l00 64 36 none detected 48 none detected Sample I was found to be the most stable and also was found to be about the largest size which could be effectively mixed with other components of dry bleach compositions. In each instance, the sample employed maintained its granulated form. A sample containing the same constituents except for the inert absorbent fused to form a solid agglomerate at the temperature employed.

EXAMPLE 2 Molten benzoic anhydride was absorbed onto several different particulate inert absorbent materials including a commercially obtained expanded perlite material. The absorbed materials were allowed to cool. The cooled materials were then compacted and ground to provide a granulated product. The various granulated materials were screened to separate particles ranging in size from about minus to plus mesh. These particles were dry blended with about half their weight of sodium perborate monohydrate. The different samples were maintained in open containers at a temperature of about 50 C. They were analyzed by infrared techniques after 4 and I0 days to determine the percent of unreacted benzoic anhydride remaining in each sample. The percent by weight of absorbent employed and results are tabulated in following table ll.

Expanded perlite 38 97 94 obtained from different commercial sources Again all the samples maintained a granulated form over the test period whereas a bleaching composition in which an inert absorbent was not employed fused into a solid mass.

In a manner similar to that illustrated in'the previous examples an organic anhydride can be dissolved in an inert volatile solvent, such as methylene chloride, and slurried with from about I00 to 200 parts by weight of an inert absorbent material, such as, for example, expanded perlite. Upon evaporation of the solvent a freeflowing powder containing the anhydride absorbed on the inert material is formed. The powder can be granulated to prepare particles of a desired size and these be employed in the production of dry bleach compositions. Also, a molten anhydride may be sprayed onto an agitated bed of an inert absorbent material. The resulting powder can be compacted and granulated to the desired particle size range.

Various modifications may be made in the present invention without departing from the spirit or scope thereof for it is understood that we are limited only as defined in the appended claims.

We claim: I

l. in a method for preparing solid dry bleaching and oxidizing granulated compositions containing at least one organic acid anhydride compound and at least one inorganic peroxygen compound said combination when dissolved in an aque ous solution yield at least one of an organic monoperacid or a persalt of an organic monoperacid as the primary bleaching and oxidizing component, the improvement which comprises: absorbing said organic acid anhydride compound onto a particulate inert absorbent material which is substantially free of uncombined water to provide a granulated product which contains from about 30 to about 65 percent by weight of said absorbent and from about 35 to about percent by weight of said anhydride absorbed thereon, and mixing said product with about an equimolar amount of said inorganic peroxygen compound to provide said bleaching and oxidizing composition, and providing said composition in particulate form having particles ranging in size from about 8 to about +20 mesh.

2. The process as defined in claim 1 wherein said inert absorbent is substantially nonhygroscopic.

3. The process as defined in claim 1 wherein said inert absorbent material is particulate expanded perlite.

4. The process as defined in claim 1 wherein said organic anhydride consists of benzoic anhydride, said inert absorbent consists of particulate expanded perlite and said granulated product contains from about 30 to about 65 percent by weight of said absorbent, and from about 35 to 70 percent by weight of said benzoic anhydride ranging in size from about minus 8 to about plus 20 mesh, and said inorganic peroxygen compound is selected from the group consisting of granulated potassium perborate, ammonium perborate, sodium perborate and mixtures thereof.

5. The process as defined in claim 4 wherein said granulated product contains from about 35 to 50 percent by weight of expanded perlite and from 50 to 65 percent by weight of benzoic anhydride. v

6. A granulated solid dry stable bleaching and oxidizing composition which when dissolved in an aqueous solution forms at least one of an organic monoperacid or a persalt thereof as the effective bleaching constituent consisting essentially of: I

a. at least one particulate inorganic peroxygen compound,

and

b. at least one particulate product said particles of said product which comprise from about 35 to about 70 percent by weight of at least one organic acid anhydride compound absorbed onto from about 30 to about 65 percent by weight of an inert absorbent material which is substantially free of uncombined water, wherein said inorganic peroxygen compound and said organic acid anhydride are provided in about an equimolar amount and the particles of said granulated composition range in size from about -8 to about .+20 mesh.

7. The solid dry bleaching composition as defined in claim 6 wherein said inert absorbent material is substantially nonhygroscopic.

8. The solid dry bleaching composition as defined in claim 6 wherein said granulated product ranges in size from about minus 5 to about plus 10 mesh.

9. The dry bleaching composition as defined in claim 6 wherein said absorbent material is expanded perlite.

10. The dry bleaching composition as defined in claim 6 wherein said organic anhydride consists of benzoic anhydride,

said inert absorbent consists of expanded perlite, said granulated product contains from about 30 to about 65 percent by weight of expanded perlite, and from about 35 to percent by weight of said benzoic anhydride and ranges in size from about minus 8 to about plus 20 mesh, and wherein said inorganic peroxygen compound is selected from the group consisting of sodium perborate, ammonium perborate, potassium perborate and mixtures thereof.

ll. The dry bleaching composition as defined in claim 10 wherein said granulated product ranges in size from about minus 8 to about plus 20 mesh and contains from about 35 to about 50 percent by weight of said particulate expanded perlite and from 50 to 65 percent by weight of benzoic anhydride.

12. A composition of matter consisting essentially of: a granulated mass of particles, each of said particles consisting of from about 30 to about 65 percent by weight of an inert absorbent material which is substantially free from uncombined water and having absorbed thereon from about 35 to about 70 percent by weight of an organic acid anhydride compound, said mass of particles ranging in size from about 8 to about +20 mesh, and said organic acid anhydride being one which when dissolved in an aqueous solution containing at least one dissolved inorganic peroxygen compound yields at least one of an organic monoperacid or a persalt of an organic monoperacid.

13. The composition as defined in claim 12 wherein said inert absorbent material is substantially nonhygroscopic.

14. The composition as defined in claim l2 wherein said particles consist of about 30 to 65 percent by weight of expanded perlite and from 35 to 70 percent by weight of benzoic acid anhydride absorbed on said expanded perlite, and said particles range in size from about minus 8 to about plus 20 mesh. 

2. The process as defined in claim 1 wherein said inert absorbent is substantially nonhygroscopic.
 3. The process as defined in claim 1 wherein said inert absorbent material is particulate expanded perlite.
 4. The process as defined in claim 1 wherein said organic anhydride consists of benzoic anhydride, said inert absorbent consists of particulate expanded perlite and said granulated product contains from about 30 to about 65 percent by weight of said absorbent, and from about 35 to 70 percent by weight of said benzoic anhydride ranging in size from about minus 8 to about plus 20 mesh, and said inorganic peroxygen compound is selected from the group consisting of granulated potassium perborate, ammonium perborate, sodium perborate and mixtures thereof.
 5. The process as defined in claim 4 wherein said granulated product contains from about 35 to 50 percent by weight of expanded perlite and from 50 to 65 percent by weight of benzoic anhydride.
 6. A granulated solid dry stable bleaching and oxidizing composition which when dissolved in an aqueous solution forms at least one of an organic monoperacid or a persalt thereof as the effective bleaching constituent consisting essentially of: a. at least one particulate inorganic peroxygen compound, and b. at least one particulate product said particles of said product which comprise from about 35 to about 70 percent by weight of at least one organic acid anhydride compound absorbed onto from about 30 to about 65 percent by weight of an inert absorbent material which is substantially free of uncombined water, wherein said inorganic peroxygen compound and said organic acid anhydride are provided in about an equimolar amount and the particles of said granulated composition range in size from about -8 to about +20 mesh.
 7. The solid dry bleaching composition as defined in claim 6 wherein said inert absorbent material is substantially nonhygroscopic.
 8. The solid dry bleaching composition as defined in claim 6 wherein said granulated product ranges in size from about minus 5 to about plus 10 mesh.
 9. The dry bleaching composition as defined in claim 6 wherein said absorbent material is expanded perlite.
 10. The dry bleaching composition as defined in claim 6 wherein said organic anhydride consists of benzoic anhydride, said inert absorbent consists of expanded perlite, said granulated product contains from about 30 to about 65 percent by weight of expanded perlite, and from about 35 to 70 percent by weight of said benzoic anhydride and ranges in size from about minus 8 to about plus 20 mesh, and wherein said inorganic peroxygen compound is selected from the group consisting of sodium perborate, ammonium perborate, potassium perborate and mixtures thereof.
 11. The dry bleaching composition as defined in claim 10 wherein said granulated product ranges in size from about minus 8 to about plus 20 mesh and contains from about 35 to about 50 percent by weight of said particulate expanded perlite and from 50 to 65 percent by weight of benzoic anhydride.
 12. A composition of matter consisting essentially of: a granulated mass of particles, each of said particles consisting of from about 30 to about 65 percent by weight of an inert absorbent material which is substantially free from uncombined water and having absorbed thereon from about 35 to about 70 percent by weight of an organic acid anhydride compound, said mass of particles ranging in size from about -8 to about +20 mesh, and said organic acid anhydride being one which when dissolved in an aqueous solution containing at least one dissolved inorganic peroxygen compound yields at least one of an organic monoperacid or a persalt of an organic monoperacid.
 13. The composition as defined in claim 12 wherein said inert absorbent material is substantially nonhygroscopic.
 14. The composition as defined in claim 12 wherein said particles consist of about 30 to 65 percent by weight of expanded perlite and from 35 to 70 percent by weight of benzoic acid anhydride absorbed on said expanded perlite, and said particles range in size from about minus 8 to about plus 20 mesh. 